Field of the Invention
The present invention relates to wireless communication, and more particularly, to a method in which a terminal receives a PHICH in a wireless communication system and a terminal using the method.
Related Art
International Telecommunication Union Radio (ITU-R) communication sector is proceeding with standardization of an International mobile telecommunication (IMT)-Advanced, a next-generation mobile communication system following the 3rd-generation. The IMT-Advanced aims at supporting Internet protocol (IP)-based multimedia services at a data rate of 1 Gbps in a stationary and low-speed movement state and at a data rate of 100 Mbps in a high speed movement state.
3rd-generation partnership project (3GPP), a system standard that meets the requirements of the IMT-Advanced, provides long term evolution (LTE)-Advanced by improving the LTE which is based on an orthogonal frequency division multiple access (OFDMA)/single carrier-frequency division multiple access (SC-FDMA) transmission scheme. The LTE-advanced is one of potential candidates for the IMT-Advanced.
In the existing LTE-A, a maximum of five carriers (cells) are aggregated to provide carrier aggregation (CA), but, in a future wireless communication system, enhanced CA (eCA) of aggregating a maximum of 32 carriers (cells) is considered. eCA may be referred to as massive CA.
When the number of aggregated carriers (cells) increases, there are several problems. For example, in an existing physical hybrid-ARQ indicator channel (PHICH) transmitting method, a PHICH resource is determined in an assumption that maximum 5 cells may be set to the terminal, but as the number of cells increases, PHICH resources may collide.
For example, the terminal may receive scheduling of a plurality of uplink cells through one downlink cell. Acknowledgement/not-acknowledgement (ACK/NACK) of a transmission block transmitted from each of the plurality of uplink cells is transmitted through PHICHs of the one downlink cell. In this case, a resource in which each PHICH is transmitted, i.e., a PHICH resource is related and determined to a specific resource of an uplink data channel to which the transmission block is transmitted, for example, a resource having a lowest resource index. When uplink data channels in each of at least two uplink cells of a plurality of uplink cells use a resource having the same resource index, a PHICH resource may collide. Accordingly, it is difficult that the terminal appropriately receives ACK/NACK of a transmission block transmitted through an uplink data channel.
As the number of cells or carriers that may be aggregated increases, a probability increases in which a PHICH resource is to collide and a method and apparatus that can solve this are required.